The present invention relates to a printing apparatus having a carriage provided with a paper guide for guiding a sheet of paper into the gap between a platen and a printing head.
Printing apparatuses are known which each comprise a cylindrical platen for holding and feeding a sheet of paper, a carriage which can move in the axial direction of the platen, and a printing head mounted on the carriage and having a plurality of dot-printing elements for printing characters on the sheet of paper supported on the platen. To set a sheet of paper around the platen of a printing apparatus of this type, the sheet is inserted into a slit formed between the upper plate of the housing of the apparatus and the platen, and extending parallel to the platen. When the platen is rotated either manually or by an electric motor, with the front edge of the sheet inserted in the slit, the sheet is guided toward the front of the apparatus along the circumference of the platen by the paper guide provided below the platen.
The front edge of the paper guide is located below the platen. Were it to protrude into the path of the carriage positioned in front of the platen, it would prevent the carriage from moving. Since the front edge of the paper guide is located below the platen, the front edge of the sheet might not pass through the gap between the platen and the printing head mounted on the carriage. To avoid this possibility, most printing apparatuses of this type have another smaller paper guide attached to the carriage, to guide the front edge of the sheet into the gap between the platen and the printing head.
The printing apparatus with two such paper guides has the following problem:
The paper guide attached to the carriage cannot be long, extending along the platen. The longer this guide, the shorter the distance the carriage can move. Inevitably, then, the guide attached to the carriage must be short. Hence, when a narrow sheet of paper is guided by the paper guide provided below the platen while the carriage is held at the leftmost or rightmost position, the front edge of the sheet may not abut on the guide attached to the carriage and, therefore, might not pass through the gap between the platen and printing head.
If this happens, the operator of the apparatus needs to rotate the platen in the reverse direction until the front edge of the sheet returns to the front edge of the paper guide located below the platen. Then, the operator manually moves the carriage to or close to the center position. Thereafter, the operator rotates the platen in the forward direction, whereby the front edge of the sheet can be guided through the gap between the platen and the printing head. However, when the carriage is manually and/or forcibly moved, its position is altered from that stored in a memory provided within the printing apparatus. In this case, the operator must firstly turn off the power supply switch and then turn it on again, in order to write the actual position of the carriage in the memory.